Why do i have red gums in front teeth and lower ones only even though i clean, floss, do scaling, and i don't even brush my gums harshly. can bruxism cause red gums in front teeth and lower ones ? please let know and what i should do?

See your local dentist for a professional cleaning. You may have built up calculus that you cannot remove by just brushing and flossing.

What's missing from your oral hygiene program is regular examinations/cleanings as well as a personalized oral hygiene review, It's more likely that your red gums are from a hygiene problem (sub gingival calculus, incorrect brushing or flossing technique, overly-aggressive brushing, wrong t'brush or t'paste, systemic disease, etc). See your Dentist/Hygienist